F#

I am learning programming, as a hobby. The software I want to study must (1) be simple enough for my old mind to understand (2) be supported by a free IDE (3) have plenty of explanatory documentation.

F#, being a Functional language, is designed to be simple. Microsoft provides a free version of its excellent Visual Studio IDE, that if it is built with the proper workloads (that do take of lot of time to install) support it directly. And there is a ton of explanatory documentation - of which Microsoft's is probably the best.